This invention relates generally to the field of air/smoke/fire dampers, and in particular, to an improved latch for use with such dampers.
It is important that an air/smoke/fire control damper be capable of withstanding intense heat and/or air pressures which may impinge on either side of the damper for substantial periods of time, such as during a fire. Due to the extreme conditions to which such dampers are subjected, it is necessary to provide blade and frame constructions which reliably combine to form a tight, positive seal capable of effectively closing off the air duct, opening or plenum with which the damper is associated, to maintain a specified fire/smoke rating.
To meet this need, a number of folding blade fire dampers have been developed. Such devices generally utilize a plurality of rotating blades which are capable of forming a seal with any adjacent blades, as well as with the damper frame. However, this seal is often prone to leakage unless relatively precise alignments and tolerances are maintained. This problem is aggravated by the fact that a smoke and fire damper must be able to function effectively in a relatively dirty environment, often years after it has been installed. Moreover, using a multiplicity of separate blades has the disadvantage of imposing a greater resistance to air flow through the damper during normal operating conditions.
In an attempt to overcome these problems, rotating blade fire and smoke dampers of the prior art are often fabricated from extremely heavy materials which are not prone to easy bending or deformation in the presence of heat. Further such damper blades are generally mounted within the damper using distinct hinges or pivots which are separately provided for the purpose of aligning each of the blades for rotational movement, and to ensure proper inter-engagement of each blade with any adjacent blades to form a seal which will not open in the presence of heat or excessive pressure. As a result, such damper constructions are often cumbersome, and relatively complex, both in operation and manufacture. Moreover, such damper constructions generally present a significant resistance to air flow, often producing unacceptable losses.
Sometimes it is desirable to provide such dampers with springs which force the blades of the damper to their closed position. My previously issued U.S. Pat. No. 3,889,156 illustrates the use of a spring in this regard. However, such springs have generally not been used in the absence of a separate locking device which directly restrains the blades during the occurance of a fire, since the heat of the fire can often cause such springs to lose their strength, and thus their effectiveness.
In therefore remains desirable to develop a damper construction which operates effectively in the presence of a fire, overcoming the foregoing disadvantages, but which provides a streamlined open blade profile capable of decreasing air flow energy losses.